In summary, a Feynman diagram is a visual representation of mathematical calculations used in quantum field theory to describe particle interactions. They are used in measurement to predict the probability of outcomes and help in understanding complex calculations. Measurements from Feynman diagrams are obtained by using mathematical formulas and equations, but they have limitations as they are based on simplifying assumptions. Alternative methods for obtaining measurements in quantum field theory include perturbation theory, numerical simulations, and experimental measurements.
Those are not measurements you do on Feynman diagrams. Feynman diagrams are not for measuring things, they are graphical representations of terms of a mathematical expression. In order to conclude this from them you need to do the math.